Electrically controlled photographic camera shutter apparatus

ABSTRACT

A camera capable of automatically determining the exposure time and having interchangeable objectives. One of the factors which determines the extent of exposure is the magnitude of the aperture through which light enters the camera. This factor is introduced either by way of one variable resistor which coacts with an objective which remains wide open and which is automatically stopped down to a preselected aperture just prior to exposure, or by way of a second variable resistor adapted to be used in the situation where the objective is not automatically stopped down just prior to exposure and instead has its diaphragm in a stopped down condition restricting travel of light passing through the objective with this light being measured after passing through the stopped down diaphragm. These variable resistors are connected in parallel and a selecting switch is provided for utilizing one or the other of the variable resistors depending upon the type of objective which is used. In addition, in order to render an electromagnet operative in the shortest possible time, the electromagnet is supplied with power not only from a conventional voltage source but also from a capacitor which is preliminarily charged.

United States Patent [.191

Miyakawa et al.

[451 July 17, 1973 [57] ABSTRACT A camera capable of automaticallydetermining the exposure time and having interchangeable objectives. Oneof the factors which determines the extent of exposure is the magnitudeof the aperture through which light enters the camera. This factor isintroduced either by way of one variable resistor which coacts with anobjective which remains wide open and which is automatically stoppeddown to a preselected aperture just prior to exposure, or by way of asecond variable resistor adapted to be used in the situation where theobjective is not automatically stopped down just prior to exposure andinstead has its diaphragm in a stopped down condition restricting travelof light passing through the objective with this light being measuredafter passing through the stopped down diaphragm. These variableresistors are connected in parallel and a selecting switch is providedfor utilizing one or the other of the variable resistors depending uponthe type of objective which is used. In addition, in order to render anelectromagnet operative in the shortest possible time, the electromagnetis supplied with power not only from a conventional voltage source butalso from a capacitor which is preliminarily charged.

4 Claims, 4 Drawing Figures ELECTRICALLY CONTROLLED PHOTOGRAPHIC CAMERASHUTTER APPARATUS [75] Inventors: Seinan Miyakawa, Nobuhiro Noda,

both of Tokyo; Mitsuhiko Shimoda, Niiza, all of Japan [73]- Assignee:Asahi Kogaku Kogyo Kabushiki Kaisha, Tokyo to, Japan [22] Filed: May 9,1972 [21] Appl. No.1 251,721

[52] US. Cl 95/53 EB, 317/123, 317/151 [51] Int. Cl. G03b 9/58, HOif7/18, HOlh 47/22 [58] Field of Search 95/10 CT, 53 E, 53 EA,

[56] References Cited UNITED STATES PATENTS 3,455,218 7/1969 Eagle et al95/53 EB 3,554,102 1/1971 Maronde 95/53 EA 3,447,031 5/1969 Jenks317/151 3,685,035 8/1972 McClain et al. 317/151 Primary Examiner-JosephF. Peters, Jr.

Attorney-Harold D. Steinberg et al.

PATENTED Jun 7 I973 sum 3 m '3 ELECTRICALLY CONTROLLED PHOTOGRAPHICCAMERA SHUTTER APPARATUS BACKGROUND OF THE INVENTION The presentinvention relates to cameras.

In particular, the present invention relates to that type of camerawhich has a circuitry for automatically determining the extent to whichfilm in the camera is exposed.

The determination of the extent of exposure is brought about in responseto exposure-determining factors among which are such factors as thelighting conditions, the size of the aperture through which the exposureis made, and the speed of the film.

It is known to determine the factor according to the lighting conditionsby measuring light traveling from the object to be photographed throughthe camera objective, after the light has passed through the objective,so that influence of the objective itself on the light is taken intoconsideration in the measurement thereof.

When using a camera of this latter type, there are two basicallydifferent types of objectives which are available with cameras which canaccept interchangeable objectives, such as single lens reflex cameras.Thus, one very well known type of objective is a so-called automaticobjective which enables the object to be photographed and the light tobe measured while the diaphragm is wide open. With an objective of thistype the diaphragm setting ring is set to provide a preselected aperturewhich is automatically achieved by automatic stopping down of thediaphragm just prior to exposure. However, such cameras also usenon-automatic objectives which must be manually stopped down to theaperture which will give a proper exposure, and when it is necessary tomeasure light which travels through such a stopped down diaphragmproblems are encountered with conventional cameras. Thus, the factor ofthe size of the exposure aperture must be added to a factor such as thelighting conditions in order to determine the proper exposure, and theaddition of these factors creates problems where objectives of the abovetwo basic types are interchangeably used.

It is also conventional with cameras of this type to utilize anelectromagnet for determining when an exposure is terminated. Thus, theshutter of such cameras is conventionally a curtain type of shutterwhere a leading curtain first moves to open the shutter while a trailingcurtain subsequently moves in order to close the shutter and terminatethe exposure. This trailing curtain is released for movement to theshutter-closing position by deenergizing the electromagnet which isinitially energized in order to hold the trailing curtain in its cockedposition in opposition to the force of springs or thelike which urge thetrailing curtain toward its closed position. This electromagnet isconventionally energized just prior to opening of the shutter. Becauseof the magnitude of the power required to bring the electromagnet to itsfully energized condition, the conventional voltage source of cameras ofthe above type is not sufficient to place the electromagnet in itsoperative, energized condition within the extremely short intervalavailable just prior to opening of the shutter. These operations inconnection with energizing of the electromagnet must take place inresponse to depression of the shutter-tripping plunger of the camera,and

during movement of this latter plunger it is necessary to energize theelectromagnet just prior to actual opening of the shutter, so that forthese reasons an extremely short interval is available for placing theelectromagnet in its operative condition. Thus, problems are alsoencountered in cameras of this type in connection with placing theelectromagnet in its fully energized condition in the extremely shorttime which is available for this purpose when using a conventionalvoltage source.

SUMMARY OF THE INVENTION It is accordingly a primary object of thepresent invention to provide a camera of the above general type whichwill avoid the above problems.

Thus, one of the objects of the present invention is to provide a cameraof the above type with the possibility of using either an automaticobjective where the diaphragm aperture is preselected with automaticstopping down taking place just prior to exposure or a nonautomaticobjective where the diaphragm is manually stopped down so that light ismeasured while traveling through the stopped down diaphragm.

In particular, it is an object of the invention to provide the circuitryof the camera with structure which will enable the factor of the size ofthe exposure aperture to be utilized in determination of the extent ofexposure with either of these different types of objectives.

Furthermore, it is an object of the present invention to provide acamera of the above type with circuitry which will enable theelectromagnet to be supplied with a sufficient amount of energy toachieve the fully energized condition in the extremely short time whichis available for this purpose, as pointed out above.

Thus, recognizing'that the electromagnet requires a large amount ofpower because of the large electromagnetic force which is required tomaintain the trailing curtain in its cocked position, it is an object ofthe invention to make available the required large power source for thepurpose of energizing the electromagnet to exert the required largeattractive force within the extremely short time which is available forthis purpose.

According to the invention the camera is provided with circuitry forautomatically determining the extent to which film in the camera isexposed, and this circuitry includes a circuit for providing a signalaccording to the magnitude of the exposure aperture. This latter circuitcomprises a first variable resistor means for introducing a signalaccording to a preselected diaphragm setting when using an objectivewhich has a wide open aperture which is automatically stopped down tothe preselected aperture just prior to exposure. This circuit furtherincludes a second variable resistor means for introducing a signalaccording to the magnitude of the exposure aperture when using anobjective which is not automatically stopped down to a preselectedaperture, so that with the latter objective light measured after passingtherethrough is restricted by the stopped down aperture. These first andsecond variable resistor means are connected in parallel with each otherand respectively include electrically conductive adjustable componentsfor determining the settings of the first and second variable resistormeans. A switch means is operatively connected with the lattercomponents for selectively connecting one or the other of thesecomponents to the circuitry.

Also, the camera has a power source electrically connected with thecircuitry thereof for supplying energy thereto, and the circuitryfurther includes an electromagnetic means for terminating an exposurewhen the electromagnetic means becomes unenergized. A switch meanselectrically connects the power source and the electromagnetic means forenergizing the latter just prior to opening of a shutter to start anexposure. A further means is electrically connected to theelectromagnetic means through this latter switch means for supplying theelectromagnetic means upon closing of the switch means with energy inaddition to that supplied only by connecting the electromagnetic meansto the power source through the switch means, so that in this way it ispossible to reduce the time lag required for energizing theelectromagnetic means to a minimum.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way ofexample in the accompanying drawings which form part of this applicationand in which:

FIG. 1 is a partly schematic wiring diagram of circuitry forautomatically determining exposure;

FIG. 2 illustrates another embodiment of circuitry for achievingautomatic as well as manually-determined exposure;

FIG. 3 is a third embodiment of circuitry, this embodiment having avoltage source checking circuit; and

FIG. 4 is a fragmentary wiring diagram of a different embodiment ofcircuitry for introducing the factor of aperture size.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 1, the circuitryillustrated therein for determining the extent to which film in thecamera is exposed includes a DCDC converter 1 having an input terminalla electrically connected by way of a conductor 30 to a DC voltagesource formed by the battery 17, this connection to the voltage sourcebeing provided by way of a main switch 16. By way of tenninals lb and1c, the converter 1 is connected to a circuit means 5 which serves tointroduce into the circuitry exposure-determining factors of the size ofthe exposure aperture and the speed of the film. This circuit means 5 isdescribed in greater detail below. However, it will be seen that thecircuit means 5 includes several variable resistor means which areconnected in parallel. As illustrated in FIG. 1 the circuit means 5 issupplied directly from the converter 1, and this arrangement is providedbecause the'current consumed by the circuit means 5 remainssubstantially constant.

Two additional circuits are energized with the output of the converter1, and these two additional circuits have a variable current demand, sothat in this case a constant voltage supply means formed by voltageregulators 6 and 7 is used, these voltage regulators also serving tocompensate for thermal variations. Thus, by way of the output terminal1d, the converter l is electrically connected to the voltage regulator6, while by way of the output terminal 1:, the converter 1 iselectrically connected to the voltage regulator 7. These regulators aswell as the converter itself are suitably grounded, as illustrated inFIG. 1. Thus, the DCDC converter ll provides a'circuit power source forthe circuit 5, this latter power source being independent of the powersource from the battery 17 which is somewhat increased or decreased toachieve output stability at the voltage regulators 6 and 7.

The circuit which is supplied from the voltage regulator 6 is alight-responsive circuit for converting the lighting conditions of theobject to be photographed into a corresponding electrical signal. Thislightresponsive means which is supplied by the voltage regulator 6includes a photosensitive element 3 which receives light from the objectto be photographed, this light first traveling through the objective ofthe camera before reaching the photosensitive means or element 3. Alsothe light-responsive means includes a diode 4 connected in series withthe photosensitive element 3 and acting as a logarithmic compressionelement.

The circuit which is supplied from the voltage regulator 7 is asignal-transmission means formed by the memory capacitor 9 which ischarged to an extent corresponding to the exposure-determining factors,and between the signal-transmission means 9 and the voltage regulator 7there is a logarithmic expansion circuit 8. This latter circuit isnormally grounded through the switch 10. This switch 10 is normallyclosed. When the shutter is opened, however, through an unillustratedmechanism the switch 10 is opened in synchronism with the opening of theshutter, so that the logarithmic expansion circuit 8 is at this timedisconnected from ground and is instead connected in series with thememory capacitor 9, upon opening of the shutter.

The several exposuredetermining factors, namely the lighting conditions,the exposure aperture magnitude, and the film speed, are added by thecircuit 5 whose output current charges the capacitor 9 through thenormally closed switch 1 1 until the terminal voltage of the capacitor 9attains the voltage level of the output from the circuit 5, thischarging operation taking place while the switches 10 and 11 remainclosed. When the tiltable mirror of the single lens reflex camera snapsupwardly beyond the path of light traveling along the optical axisthrough the objective, immediately ,prior to opening of the shutter, theswitch 11 simultaneously opens, with the switch 10 also openingsimultaneously with the opening of the shutter, as referred to above, sothat the charging of the signal-transmission means 9 with the signals tobe used in determining the exposure continues from the time when thecamera is directed toward the object to be photographed (actually fromthe time when the main switch 16 is closed) until the time when theswitch 11 opens.

The junction between the switch 11 and the signaltransmission means 9and a switching circuit means 12, referred to in greater detail below,are interconnected by way of a resistor 9a, so that through thisresistor the signal-transmission means 9 is connected with the switchingcircuit means 12. An indicating means 13, in the form of a suitablemeter, is connected in parallel with the switching circuit means 12.This switching circuit means 12 has at its output a transistor 14 whichis connected at its base to the remainder of the switching circuit means12, and through the transistor 14 the switching circuit means 12 isconnected to the voltage source 17 through a circuit which is thuscontrolled by the transistor 14. This latter circuit includes not onlythe energizing source 17 but also the main switch 16, which isautomatically closed during the initial increment of movement of theshutter-tripping plunger, before the shutter is actually tripped, aswitch 15 connected in series with the switch 16 and automaticallyclosed in a known way just prior to opening of the shutter as the mirroris snapped upwardly, and an electromagnetic means 2 which is connectedin series between the transistor 14 and the switch 15. Thiselectromagnetic means 2, when it is deenergized, will in a known wayrelease a trailing curtain of the shutter so that the trailing curtainwill run down to its rest position for closing the shutter. Thus, theelectromagnetic means 2, the switch 15, and the switch 16 are connectedin series between the transistor 14 and the battery 17.

The circuit 5 for adding the exposure-determining factors includes threevariable resistor means 19,20, and 21. These three variable resistormeans are connected in parallel between the terminals lb and 1c of theconverter 1. It will be noted that the lightresponsive means formed bythe circuit which includes the components 3 and 4 is connected from thejunction 32 between the components 3 and 4 through a changeover switchmeans 18 to one or the other of the variable resistor means 19 and 20,so that in this way the exposure-determining factor of the lightingconditions at the object to be photographed is added to the otherfactors of the magnitude of the exposure aperture and the film speed,these three factors forming when added together the signal which issupplied to the signal-transmission means formed by the memory capacitor9. Thus, the signal according to the lighting conditions is added, inthe position of the parts shown in FIG. 1, by way of the switch 18 tothe aperture magnitude signal derived from the variable resistor whichis connected in parallel with the variable resistor means 21 whichprovides the film speed signal, so that these three signals are combinedto form the output of the circuit 5 which is delivered to the capacitor9 while energizing takes place by way of the independent constantvoltage from the converter 1. The magnitude of the signals will dependupon the intensity of the light received by the photosensitive element 3as well as the positions of the movable electrically conductivecomponents of the variable resistor means 20 and 21. In this way thecharging of the memory capacitor 9 is regulated in accordance with theexposure-determining factors.

The variable resistor means 20 is in the form of a potentiometer havinga slidable contact which forms the electrically conductive componentcorinected to the switch 18 in the position of the parts shown inFIG. 1. This variable resistor means 20 is adapted to be used with anobjective which is automatic in the sense that it remains wide open andis automatically stopped down to a preselected aperture just prior toexposure. Such objectives are well known. The objective has an aperturesetting ring which is turned to set the diaphragm for providing apredetermined aperture just prior to exposure. When this ring is turnedthrough an unillustrated transmission the slider of the potentiom eter20 is shifted along the potentiometer to introduce into the circuit thefactor of the size of the exposure aperture. The sliding contact of thepotentiometer 21 is moved in the same way by way of a ring which is usedto introduce into the camera a value corresponding to the speed of thefilm which is exposed. In this way the variable resistor means 21 willintroduce a signal according to the film speed. The voltage controlfunction achieved with these potentiometers 20 and 21 is such that avariation of the preselected lens aperture value corresponding to onegraduation of the diaphragm setting ring and a variation of the filmspeed value corresponding to one graduation of the speed setting ringare maintained in correspondence with a variation of the light intensityby one incremental value such as one light value. Therefore, the outputof the circuit 5 is a voltage corresponding to the added informationderived from the light intensity at the object to be photographed, thepreselected aperture magnitude, and the film speed.

The diaphragm setting ring will, as is well known, determine the size ofthe aperture through which the film is actually exposed. However, thisring does not actually stop the diaphragm down to a positioncorresponding to the setting of the ring. This latter stopping down ofthe diaphragm is brought about automatically just prior to exposure, aspointed out above. For this purpose the diaphragm setting ring of suchan automatic objective is coupled to the sliding contact of thepotentiometer 20 in such a way that a pawl or other motiontransmittingelement which moves together with the diaphragm setting ring extendsfrom the lens barrel of the objective into the interior of the camerahousing to transmit the motion to the sliding contact of thepotentiometer 20. Thus, in order to obtain this type of coupledoperation an automatic objective has a special structure fortransmitting the motion from the diaphragm setting ring to thepotentiometer.

However, it is also possible to use with a camera such as a single lensreflex camera a single stage lens which is commercially available andwhich must be manually stopped down to the required aperture since suchlenses do not have motion-transmitting elements which extend into thecamera for preliminarily setting a potentiometer to a setting whichcorresponds to a selected aperture. When such a non-automatic, manuallyadjustable objective is used with the camera, measurement of the lightwhich travels through the objective takes place in a restricted mannerthrough an aperture which has already been stopped down to the selectedvalue. During light measurement through such a stopped down aperture, itis not possible to obtain a useful function from the potentiometer 20and if the potentiometer 20 is used in determining the extent ofexposure there will be an unavoidable error, this error occurring ofcourse in thelight measurement.

In the example shown in FIG. 1, the change-over switch means 18 normallyassumes a position engaging the contact 18b of the adjustable componentof the potentiometer or variable resistor means 19. The projection fromthe automatic objective, when the latter is mounted on the camera,serves not only to transmit movement from the diaphragm setting ring tothe adjustable component of the variable resistor means 20, but also todisplace the switch 18 to the position shown in FIG. 1 where it engagesthe contact 18a of the adjustable component of the variable resistormeans 20. Therefore, when using a non-automatic objective which must bemanually stopped down, the information or signal with respect to thelight intensity is added to the variable resistor 19. This secondvariable resistor means 19 has its movable adjusting component fixed bythe manufacturer after displacement to a position establishing acondition according to which the resistance value provided by way of thepotentiometer or variable resistor means 19 corresponds to theresistance which would be derived from the potentiometer 20 with thelatter short-circuited or bypassed.

In this connection, such a circuit arrangement is shown in theembodiment illustrated in FIG. 4 which differs from that of FIG. 1 onlyin that the potentiometer or variable resistor means 20 is indeedprovided with such a bypass switch means 22, as referred to above. Thus,it will be seen from FIG. 4, that the bypass switch means 22 isconnected between the potentiometer 20 and the slidable contact thereof,so that when the switch 22 is closed the potentiometer is bypassed insuch a way that it achieves a constant voltage control functionirrespective of the position of the sliding contact. This switch 22 is anormally closed switch. The motion-transmitting element carried by theautomatic objective will act on this switch 22 in order to open it onlywhen such an automatic objective is used. Therefore a manuallyadjustable objective, which is to say an objective which must have itsdiaphragm manually stopped down, will not influence the switch 22 whichthus remains closed when using such an objective. Therefore in theclosed position of the switch 22 the potentiometer 20 provides aconstant voltage control function irrespective of the position of itssliding contact. The resistance value achieved from the potentiometer 20at this time corresponds to that which is achieved from thepotentiometer 19 when its slidable contact is fixed by the manufacturer.This potentiometer 19 is useful in measuring the light even through anautomatic objective when the latter is in a condition where itsdiaphragm is actually stopped down.

Thus, with the above structure of FIGS. 1 and 4, when the change-overswitch means 18 engages the contact 18a, light measurement is madethrough a wide open objective with the diaphragm setting beingpreselected but not actually achieved until automatic stopping downtakes place just prior to exposure. On the other hand, when thechange-over switch means 18 engages the contact l8b, it connects intothe circuit the variable resistor means which is adapted to cooperatewith an objective which must be manually stopped down with lightmeasurement taking place through the restriction provided by the stoppeddown diaphragm. Of course, this type of operation is also effective evenwith an automatic objective after the diaphragm thereof is stopped down.It is to be noted that when the switch means 18 engages the contact 18b,the potentiometer 20 is disenabled even if the switch 22 is opened,

so that it is indeed possible to carry out light measurement through astopped down objective even if this objective is of the type whichnormally is automatically stopped down just prior to exposure. In otherwords it may sometimes happen that an automatic objective is used insuch a way that its diaphragm is already in a stop-down condition duringmeasurement of light, and even in this case the circuitry of FIGS. 1 and4 will operate properly.

Thus, the exposure-determining factors supplied to the circuitry throughthe above-described signal supply 1 means arestored in the fonn of anelectrical charge in light which has passed through the objective andwhich is reflected by the tiltable mirror, so that when the latter hasswung upwardly beyond the optical axis there is no longer anyimpingement of light on the element 3 from the object which is to bephotographed.

The switching circuit means 12 receives from the signal-transmission 9the signal corresponding to the addition of the exposure-determiningfactors as described above. This switching circuit means 12 includes afield effect transistor 42 of high input impedance and a variableresistor 23 connected to the output terminal of the transistor 42, thisvariable resistor 23 also forming a potentiometer having a slidingcontact 24. This contact 24 forms part of a mechanism referred to belowwhich operates in a mechanical way to bring about an exposure time ofextremely short duration. The switching circuit means 12 furtherincludes a switching element 25 such as a thyristor for controlling thedeenergizing of the electromagnetic means 2, and the sliding contact 24of the variable resistor means 23 is electrically connected to thecontrol electrode of the thyristor 25.

The switch 15 is automatically closed just before the shutter is opened,while the tiltable mirror snaps upwardly, and at this instant the chargestored in the memory capacitor 9 is insufficient to render the switchingelement 25 conductive. Therefore, the transistor 14 remains in itsconductive state to maintain the electromagnet 2 in its energizedcondition. As a result the electromagnetic means 2 holds the elementswhich are required to be released in order to permit the shutter toclose, and thus these elements are prevented from operating even beforethe shutter opens, when the electromagnetic means 2 is energized byclosing of the switch 15.

The circuitry includes an additional field effect transistor 26connected in parallel with the field effect transistor 42. An indicatingmeans 13, in the form of a suitable meter such as an ammeter, isconnected to the transistor 26 in parallel with the output loadresistance 27 thereof. This indicating means 13 takes the form of anexposure meter structure in which an ammeter is utilized as theindicating instrument.

During transmission of the signal from the memory capacitor 9 to theswitching circuit means 12, the transistor 26 controls the electriccurrent which flows therethrough in accordance with the magnitude of thesignal. Thus, the transistor 26 will serve to reliably transmit thesignal stored in the capacitor 9 to the indicating means 13 in the formof a meter which is controlled in accordance with the magnitude of thesignal. This structure for giving an indication of the result of themeasurement of the light and the addition of the otherexposure-determining factors includes the transistor 42 of high inputimpedance which forms the input for the switching circuit means 12 andthe separate parallel-connected transistor 26 of high input impedance,so that the switching circuit operation with this circuitry iscompletely free of any electrical disturbance from the indicating means13 which otherwise would occur if the parallel connection through theseparate transistor 26 were not provided. Therefore the operation of theswitching circuit means 12, on the one hand, and the indicating means13, on the other hand, never interfere with each other. The value whichis indicated by the indicating means 13 corresponds to a shutter speed,and this indicating means 13 may be provided with a scale of shutterspeeds having graduations which cooperate with the movable pointer sothat the operator can directly read from the meter 13 the exposure timewhich will be provided by the circuitry, this exposure time beingdirectly measured in seconds on the scale at the meter 13 andcorresponding to the magnitude of the signal which is transmitted to theswitching circuit means 12 by the signal-transmission means 9. Theindication given by the indicating means 13 is provided through asuitable switch which becomes closed automatically during the initialpart of the depression of the shutter-tripping plunger, before theshutter is actually tripped, so that after slight depression of theshutter-tripping plunger it is possible to measure at the meter 13factors such as the light at the object to be photographed, and theoperator may hold the shutter-tripping plunger in a partially depressedcondition in order to preliminarily see at the meter 13 the value of theshutter speed which will be provided by the circuitry if the depressionof a shutter-tripping plunger is continued to actually trip the shutter.

During the further depression of this shutter-tripping plunger thetiltable reflector is snapped upwardly in a known way, and the switch 11is automatically opened through a suitable transmission during theinitial part of the depression of the shutter-tripping plunger. Thememory capacitor 9 thus remains in its condition corresponding to thatwhich results just prior to opening of the switch 11. The tiltablemirror snaps upwardly and then with the completion of the depression ofthe shutter-tripping plunger the shutter opens.

In synchronism with the opening of the shutter the switch opens, and asthis switch 10 opens the capacitor 9 is additionally charged through thelogarithmic expansion circuit 8 from the voltage regulator 7. Then theinput voltage of the-switching circuit means 12 attains the level atwhich the switching circuit 12 transfers to a conductive state as thecharging of the capacitor 9 continues, and thus the switching circuit 12will suddenly transfer to a state of electrical continuity orconductivity. Therefore, the duration of the interval from the start ofthe additional charging through the logarithmic expansion circuit 8 tothe transfer of the switching circuit means 12 to the state ofelectrical conductivity corresponds to the timing signal which determines the duration during which-the shutter remains open, or in otherwords the duration of the exposure. The manner in which such a timingvalue is achieved is described in detail in copending application Ser.No. 28,457, filed Apr. 14, 1970 so that it is not described further.

It is possible to achieve control of relatively long exposures, forexample longer than 1/500 sec., with extremely great precision throughthe operation of the above circuitry by corresponding regulation of theswitching level of the switching element 25. However, control of shorterexposures where the exposure time is at an extremely high speed range onthe order of l/ 1,000 sec., for example, tends to be unstable due tofactors such as the time lag in the operation of the electromagnet 2. Amechanical shutter control mechanism may be operated preliminarily toachieve an effective control with extremely short exposure times incases such as the photographing of objects which move at high speed.Under these conditions control of the shutter by the electricalcircuitry which includes the switching circuit means 12 should beavoided so that this switching circuit means should not operate at thistime. This type of operation is achieved by deenergizing theelectromagnet 2 so that it will release the trailing curtain and thusterminate the exposure.

For this purpose, there is provided at the switching circuit means 12 acontrol means which controls the electromagnet in order to achieve, in amechanical way, an extremely short exposure time. This control meansincludes the sliding contact 24 of the variable resistor 23 which forthis purpose assumes a position displaced along the resistor 23 to alocation where a bleeder voltage is produced at the sliding contact 24in association with the change-over from electrical control tomechanical control. The arrangement is such that this bleeder voltage issufficiently positive and of such a magnitude that it is great enough totransfer by itself the switching element 25 to the conductive state atthe instant when the memory capacitor 9 is completely charged.

Thus, through the control achieved with ableeder voltage resulting fromthe displacement of the contact 24 in association with the thyristor 25it is possible to achieve in a mechanical way a deenergizing of theelectromagnet 2 suitable for high speed operation where an extremelyshort exposure time is required.

During normal operation with longer exposure times, the switchingelement 25 transfers to its state of electrical conductivity and thevoltage on the anode side thereof drops sharply. A Zener diode 26 isinserted between the anode of the thyristor 25 and the base of thetransistor 14. As long as the thyristor 25 is in a nonconductive state,the Zener diode 26 is in its conductive state since the Zener diode 26is provided with voltage higher than its Zener voltage as a result ofenergizing of the Zener diode 26 from the voltage regulator 6. At theinstant when the element 25 transfers to its conductive state the Zenerdiode transfers to its nonconductive state since the input voltage tothe diode 26 will drop instantaneously at this time.

The transistor 14 transfers to its non-conductive state only underregulation of the magnitude of the control signal from the Zener diode26 which is connected to the control electrode of the transistor 14,this operation taking place without any delay due to the counterelectromotive force generated when the electromagnetic means 2 connectedin series with the switching transistor l4 and serving to initiate theshuttebclosing operation is deenergized. More specifically, thistransistor 14 transfers completely to its state of electricaldiscontinuity when the control signal to the transistor 14 isinstantaneously eliminated by the Zener diode 26 according to the signalfrom the switching element 25 at the instant when the latter becomesconductive. in this way the electromagnetic means 2 becomes deenergizedso that the trailing curtain is released from the holding effect of theelectromagnetic means 2 and starts to run in order to terminate theexposure by closing the shutter.

The circuitry provides a highly efi'ective operation of theelectromagnetic means 2. This electromagnetic means 2 which has a highpower requirement is energized by way of the switch 15 just prior toopening of the shutter. The instant when the electromagnetic means 2 isenergized is selected in such a way that the duration of operation ofthe electromagnetic means 2 is reduced to a minimum. Therefore, theswitch 15 is not closed until the final moment before opening of theshutter, so that in this way the electromagnetic means 2 will reliablyhold the trailing curtain but at the same time will be maintainedenergized for a minimum duration. Accordingly, it is important to reduceto a minimum the time lag from the instant of closure of the switch 15to activation of the electromagnetic means 2. This result is effectivelyachieved by supplying a large quantity of electricity to theelectromagnetic means 2. The battery 17 itself, however, has an internalresistance, with the result that it is difficult to provide a largequantity of electricity instantaneously. With the circuitry disclosed inFIG. 1, however, a capacitor 4th is connected through the main switch 16in parallel with the battery 17, and the capacitor 40 will have itsdischarge circuit established through the electromagnetic means 2 uponclosing of the switch 15. Thus, the capacitor 40 forms a means forsupplying to the electromagnetic means 2 power in addition to that whichis derived directly from the battery 17 upon closing of the switch 15.Prior to closing of the switch 15 the capacitor 40 is preliminarilycharged from the battery 17 through the main switch 16 which is closedprior to closing of the switch 15. Thus, the charge which has beenstored on the capacitor 40 is discharged to the electromagnetic means 2at the instant when the switch 15 closes and the electromagnetic means 2is accordingly sufficiently energized by the additional energy from thecapacitor 40 as well as the energy from the battery 17 to achieve aninstantaneous activation of the electromagnetic means 2. In this way theabove time lag is very substantially reduced.

In addition, while a DC current is supplied to the electromagnetic means2 from the battery 17, a feeble AC component is applied to the circuitwhich energizes the electromagnetic means 2 from the DC-DC converter lbyway of the circuit which connects the battery l7 and the converter 1to each other, so that in this way a rippled direct current composed ofan AC output and the output from the battery 17 is supplied to theelectromagnetic means 2. This rippled current effectively acts upon theelectromagnetic means 2 when the transistor 14 is turned off. The rippleform of current acts so that it is possible for an electromagneticallyattractive force generated due to magnetic hysteresis of theelectromagnetic means 2, upon deenergizing thereof, to be rapidlycounteracted by the ripple current as the switching circuit means 12transfers to the electrically conductive state and the transistor 14completely transfers to the electrically non-conductive state.Accordingly, upon deenergizing of the electromagnet 2, its holdingeffect on the trailing curtain is immediatelygiven up and shutterclosing takes place instantaneously without any possible delay of thetype referred to above.

Thus, this circuitry for controlling the electromagnetic means 2 isuseful to reduce the time lag with respect to the moment when theelectromagnetic means 2 is energized as well as the time lag withrespect to the instant when the electromagnetic means 2 is deenergized,with time lags at both of these instants being reduced to a minimum soas to bring about a highly effective precision in the operation.

In the embodiment described above the memory capacitor9 is charged withthe output from the exposuredeterrnining factor adding'circuit 5, andthe exposure time is automatically determined according to the factor oflight intensity and the additional factors added by the circuit 5. Withthe embodiment of FIG. 2, the switch 11 has the form of a change-overswitch serving to selectively connect into the circuit either thesignalsupply means formed by the circuit 5 and the lightresponsivecircuit or an additional manually operable signal-supply means formed bycomponents 30-32 and connected to the contact 11b of the change-overswitch 11 of FIG. 2. The contact 11a of this change'over switch servesto transmit to the circuitry the signals from the signal-supply meansreferred to above.

The manually operable signal-supply means 30-32 supplies a bleedervoltage output terminal 32 of the bleeder circuit 31 which is connectedto its own independent power source 30. The output terminal 32 ismovable relative to the bleeder resistance 31 so that the output voltagecan be manually determined. This manual determination of the magnitudeof this output voltage may be brought about by turning a suitable dialwhich is displaced in accordance with shutter speed graduations.

Thus, when the operator selects to manually determine the exposure time,the switch 11 will be placed in engagement with the contact 1 lb, andnow the capacitor 9 is charged to the level of the bleeder outputvoltage of the manually operable signal-supply means. When the bleederoutput voltage is that resulting from operation in accordance with aselected shutter speed graduation, the information or signal stored inthe capacitor 9 takes a value corresponding to this graduation and theselected shutter time corresponding to the selected graduation isachieved by additional charging in precisely the same way as duringautomatic control in the manner described above. In this way it ispossible to achieve with the embodiment of FIG. 2 a manually selectedexposure time while utilizing only a minimum amount of additionalstructure with the same controls, except for the signal supply means,being used both for automatic and manual exposure time determination.

The embodiment of FIG. 3 corresponds to those described above except forthe following differences. This embodiment includes a manually operableswitch 33 for opening and closing a checking circuit means capable ofchecking the condition of the voltage source 17. The normally openmanually operable'switch 33 serves to connect the battery 17 to aresistor 34 of the checking circuit, this resistor 34 being connected inseries with a resistor 35 which in turn is connected with a diode 36inserted in a forward direction with respect to the battery 17 whichserves as a DC power source. These components of the checking circuitmeans are connected in series between the battery 17 and the inputterminal 13a of the indicating means 13. The checking circuit meansfurther includes a thermal compensating element 37 and adjustingresistances 38 and 39 which are connected in parallel with theresistance 35, the diode 36, and the indicating meter 13 so as toachieve in this way a voltage checking circuit for determining thecondition of the battery 17 as the DC power source.

During checking of the voltage of the battery 17, the

switch 33, which normally remains open, is manually closed. Of course,before closing the switch 33 the main switch 16 is opened so that therewill be no interference with the checking of the condition of thebattery 17 from the remainder of the circuitry. Closing the switch 33initiates the energizing of the indicating means 13 through theresistances 34 and 35 and the diode 36 from the battery 17, so that thevoltage of the battery 17 may be reliably checked through reading thisvoltage which is indicated at a suitable scale of the meter 13 underregulation of the thermal compensating element 37. The diode 36 providedfor checking of the voltage of the battery 17 as a DC power source isinserted in the forward direction with respect to the battery 17 so thatthe operation of the voltage checking circuit will have no influence onthe operation of the indicating means 13 when the switch 33 is opened.Thus the same meter 13 can be used for preliminarily indicating to theoperator the exposure time which will be automatically achieved, aspointed out above, as well as for battery checking purposes, without thechecking circuit having any influence on the meter 13 when the switch 33is open. Therefore, during measurement such as light measurement tocontrol the electric shutter the battery checking circuit will have noundesirable influence as a result of the diode 36.

Thus, the above circuitry assures a highly reliable operation byproviding the above checking circuit which enables the battery 17 to bemaintained in proper operating condition, as well as by providing amulti-source system formed by the DC-DC converter 1 and the voltageregulating means 6 and 7 in each load circuit which is likely to bethermally influenced inan undesirable manner.

What is claimed is:

1. In a camera having circuitry for automatically determining the extentto which film in the camera is exposed, a power source electricallyconnected with said circuitry for supplying energy thereto, saidcircuitry including an electromagnetic means for terminating an exposurewhen said electromagnetic means becomes unenergized, switch meanselectrically connected between said power source and saidelectromagnetic means for energizing the latter just prior to opening ofa shutter to start an exposure, and means electrically connected to saidelectromagnetic means through said switch means for supplying saidelectromagnetic means upon closing of said switch means with energy inaddition to that supplied only by connecting said electromagnetic meansto said power source through said switch means for reducing the time lagrequired for energizing of said electromagnetic means to a minimum.

2. The combination of claim 1 and wherein said means connectedelectrically to said electromagnetic means through said switch means forproviding said additional energy is a capacitor means.

3. The combination of claim 2 and wherein a second switch means iselectrically connected between said capacitor means and said powersource for charging said capacitor means prior to closing of saidfirst-mentioned switch means.

4. The combination of claim 3 and wherein said second switch means isconnected in series between said first-mentioned switch means and saidpower source, said first-mentioned switch means being connected inseries between said second switch means and said electromagnetic means,and said capacitor means being electrically connected to a junctionbetween both of said switch means.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO.3,745,901 Dated July I 17, 1973 Inventor(s) Miyakawa! n n, 8t Ell.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

In the heading, between items [21] and [52] insert:

[30] Foreign Application Priority Data 1 J P n.....l97l'-38l82 y 19.1971 Ja an. .-....1971-39719 Signed and sealed this 10th day o DecemberI97 zittGSt: I'IcCOZ 1. GIBSON c. Z-IARSHALL DANN Attesting OfficerComissioner'of Patents FORM po'wso H0459) USCOMM-DC acme-ps9 USGOVERNMENT FRlNTlNG OFFICE t 1959 O366-33 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,745,901 Dated July 17, 1973Inventor(s) ivliyakavjal Seinan: et l- It is certified that errorappears in the aboveidentified patent and that said Letters Patent arehereby corrected as shown below:

In the heading, between items [21] and [52] insert: v a

[30} Foreign pplication Priority Data y 1971 aa anuu. .1971-38182 y 1971p n. .....1971- 39719 Signed and sealed this 10th day 01 December E974.

En-*2 L fattest:

mess: 2'1. smsoN JR. c. IiARSHALL DANN *i-ttesting Offier Commissioner'of Patents FCRM [DO-1050 no'sg) USCOMM-DC 60376-P69 I Q US. GOVERNMENTPRINTING OFHCE I l, 36$- 33l

1. In a camera having circuitry for automatically determining the extentto which film in the camera is exposed, a power source electricallyconnected with said circuitry for supplying energy thereto, saidcircuitry including an electromagnetic means for terminating an exposurewhen said electromagnetic means becomes unenergized, switch meanselectrically connected between said power source and saidelectromagnetic means for energizing the latter just prior to opening ofa shutter to start an exposure, and means electrically connected to saidelectromagnetic means through said switch means for supplying saidelectromagnetic means upon closing of said switch means with energy inaddition to that supplied only by connecting said electromagnetic meansto said power source through said switch means for reducing the time lagrequired for energizing of said electromagnetic means to a minimum. 2.The combination of claim 1 and wherein said means connected electricallyto said electromagnetic means through said switch means for providingsaid additional energy is a capacitor means.
 3. The combination of claim2 and wherein a second switch means is electrically connected betweensaid capacitor means and said power source for charging said capacitormeans prior to closing of said first-mentioned switch means.
 4. Thecombination of claim 3 and wherein said second switch means is connectedin series between said first-mentioned switch means and said powersource, said first-mentioned switch means being connected in seriesbetween said second switch means and said electromagnetic means, andsaid capacitor means being electrically connected to a junction betweenboth of said switch means.